What would be the best way of describing the art of the early 20th century

I've told you that one of the best ways to understand a society is to look at the art, music, and literature it produces.  Looking at the Baroque style tells you a lot about what is going on in the17th century.  Looking at the Rococco and Neo-Classical/Classical styles of the 18th century tells you a lot about that time period.  Looking at the Romantic and Realistic styles of the 19th century also tells you a lot about that century. 

The artistic styles of the 20th century likewise tell you a lot about that century.  The problem is that their are dozens of different styles and movements in the arts in the 20th century, not just one or two that typify the century.  Nevertheless, regardless of style, one can point to three particularly distinctive trends in much (though certainly not all) 20th century art, music, and literature:
A tendency to be less and less accessible to average personA tendency to glorify art itselfA tendency to undercut traditional standards and values

hope this helps